Here are some examples of answers:
1. A song was sung by Rita.
2. A restaurant was opened last year by them.
3. An interesting story was told by granny.
Now use these, and this website: https://webapps.towson.edu/ows/activepass.htm
to help you with the rest.
The way I like to remember it, is to take the first noun and the second noun and switch them, then alter the verb tense and sentence structure to make it make sense.
Answer:
1 show, sign 2. critical 3 definitions 4 circular
